#include <stdio.h>
//g++ -o c_copyfile c_copyfile.cc
int main(int argc, char** argv) {
	FILE* src_file = fopen64(argv[1],"a+");
	int len = 0;
	char buf[10] = "leiyxsb";

	fseek(src_file, SEEK_CUR, 1);
	printf("%ld",ftell(src_file));
	fread(buf, 1, 3, src_file);
	printf("%ld",ftell(src_file));
	fwrite(buf, 1, 5, src_file);
	printf("%ld",ftell(src_file));
	printf("%s",buf);
	fclose(src_file);
}
//./c_copyfile b.txt c.txt